Analysis Of Interaction Among Humic Acids, Aluminum Sulfate And Some Inorganic Pollutants In Water

As to the general goal of environment analysis and sewage management, this thesis mainly studied the interaction among humic acids, aluminum sulfate and some inorganic pollutants in water. On this basis, it studied the probability of the synergistic effect's practical application on the treatment of inorganic pollution in water samples. First of all, the synergistic effect of humic acids and aluminum sulfate on heavy metal ions (Pb²⁺,Cd²⁺,Cu²⁺) removal were studied. Second, removals of fluoride by aluminium sulfate coagulant in the presence of humic acids were studied. The main contents are listed as follows:1. The removal of heavy metal ions from solution, such as Pb²⁺, Cu²⁺ and Cd²⁺, was studied by binding the ions to humic acids (HA) and then coagulating-flocculating with aluminum sulfate (AS) flocculant. The effect of the dosage of AS, the pH level, and the concentrations of HA and metal ions were studied. The highest removal efficiencies of HA by AS flocculant are all above 97% in the optimum AS dose region under different pH. The metal ions binding to the humic acids do not affect the removal efficiency of humic acids, but increasing the heavy metal concentration leads to a decrease in the required amount of AS for flocculation. The high removal efficiency of metal ions can be achieved under strictly controlling the effective flocculation region. The pH affects the removal efficiency of bound (complexed) metal, in so much as it affects the binding strength of metal ions to the HA. A possible mechanism of flocculating metal-HA by aluminum sulfate is proposed based on experiment results. The results indicated that such a complexation-flocculation process is of potential application for the removal of heavy metal ions during water treatment.2. Excess of fluoride (>1.5 mg/L) in drinking water is harmful to the human health. Using aluminium sulfate as a model coagulant, removal of fluoride by coagulation was investigated in the absence or presence of humic acids in synthetic water. Results demonstrated that in synthetic water, 80.71-85.86% removal efficiency of fluoride was achieved in the absence of HA with 2-10mg/L coagulant when fluoride initial concentration was 2 mg/L, while 65.69-85.44% removal efficiency of fluoride was obtained in the presence of HA with the same coagulant dosage. Whereas, when improving fluoride initial concentration, HA apparently reduced sharply the removal of fluoride with low coagulant dosage or at high pH, while minor influence on removal of fluoride was observed with high coagulant dosage or at low pH. Thus, fluoride could be reduced effectively by humic acids in drinking water treatment. Meanwhile, fluoride reduced the removal of HA at high pH and with low coagulant dosage.